How to Calculate a Date 30 Days After an Earlier Date in a PDF Form
Question details
The user needs to use custom JavaScript to compare two manually entered dates in a PDF form and output a date exactly 30 days after the earlier of the two dates.
- Product
- PDF Editor / Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Setting up a dynamic PDF form that requires automated date calculations based on user input from multiple date fields.
- Observed behavior
- Automatically identifying the earlier date from two fields, adding 30 days to it, and displaying the formatted result in a target field, while remaining blank if inputs are missing.
Ensure you are using a PDF editor with advanced form editing capabilities and JavaScript support. Note down the exact names of your two source date fields before writing the calculation script.
Use Custom JavaScript to Calculate the Date
Add a custom calculation script to a destination text field to read the source dates, compare them, and add 30 days to the earlier date.
PDF forms use JavaScript for advanced custom calculations. By reading the date fields as strings and converting them to JavaScript Date objects using the util.scand() method, you can easily compare their exact time values.
Open your PDF form in editing mode. Right-click the destination text field where you want the calculated date to appear, select 'Properties', and navigate to the 'Calculate' tab.
Select 'Custom calculation script' and click 'Edit'. Begin by assigning the values of your two date fields to variables using getField('FieldName').valueAsString.
Use util.scand('mm/dd/yy', variableName) to convert the extracted strings into Date objects. Make sure the format string 'mm/dd/yy' matches the exact format used in your source date fields.
Use the getTime() method to compare the two Date objects and determine which is earlier. Once the earlier date is identified, add 30 days to it using setDate(date.getDate() + 30).
Format the newly calculated date using util.printd('mm/dd/yy', date) and assign it to event.value. Include an 'else' condition to set event.value = '' (an empty string) if neither field contains a valid date, keeping the field blank.
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- 1. Open PDF in WPS Office: Launch WPS Office and open your interactive PDF form document.
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Frequently Asked Questions
Why is my PDF date calculation script returning a blank field or an error?
This typically happens if the field names in your JavaScript do not exactly match the actual field names in your PDF form, or if the date format entered by the user doesn't match the format specified in your util.scand() function.
How do I change the date format from mm/dd/yy to dd/mm/yyyy?
You can change the date format by updating the format string parameter in both the util.scand('dd/mm/yyyy', value) and util.printd('dd/mm/yyyy', date) functions within your custom calculation script.
Can I add 60 days instead of 30 days to the earlier date?
Yes. In the custom calculation script, locate the line where the date is modified (e.g., d.setDate(d.getDate() + 30)) and simply change the number 30 to 60 or any other number of days you require.
